IR Suppression System for Naval Platforms

lnfrared (IR) radiation is one of the vital stealth signature that needs to be minimised to conceal the naval vessels from IR-guided missiles. The ship signature levels depend upon the uptake of plume and metal surface temperatures, ambient conditions (background sea and sky), and ship hull and structure temperatures. To minimise the engine exhaust, DRDO has designed and developed an lnfrared Suppression System (IRSS) for diesel engines using eductor diffuser principle with film cooling rings, where the eductor action provides suction effect by maintaining vacuum at higher velocities.

The system entraps ambient cool air and mixes it with exhaust plume to reduce its temperature. ln addition, intermediate film cooling slots have been provided for continuous thermal insulating of ambient cool air to minimise direct heat transfer.

The system mainly comprises a nozzle, mixing tube, and a three-ring diffuser. The main aim of suppressing the IR signature is to eliminate the high contrast radiance sources and make naval platforms appear as an extended low IR radiance object to merge with ambience. Design of IRSS is associated with aero-thermal calculations, heat transfer, fluid dynamics, and structural analysis. CPD analysis was employed to mimic the flow configuration, estimation of secondary air entrainment, film cooling effect, system metal surface and exhaust plume temperature ranges, etc. 1:1 full- scale experimental studies were carried out for diesel engine to estimate performance of the system. At 100 per cent operational conditions, 85 per cent reduction in the temperature levels of exhaust metal surface has been achieved.